conhost.exe seemingly leaking memory

Question

I have a .NET Framework ASP.NET application running in IIS. The application launches a long-lived sub-process but is otherwise unremarkable (just one endpoint which effectively proxies requests to the sub-process).

While the system is serving requests, the memory usage for conhost.exe on the machine steadily rises (~linear growth); after about a day it will be consuming .5-1 GB. Every 29 hours, the IIS application pool automatically recycles itself; at this point the conhost usage drops back to zero but then starts steadily growing again.

What could cause conhost to use this much memory?

UPDATE:

I saw that the settings for Console.BufferWidth and Console.BufferHeight can lead to more memory usage in conhost.exe. Therefore, I added logging for these values. However, my app shows a constant small buffer width and height.

UPDATE:

Per @simon-mourier's comment we pulled the dlls attached to the conhost process. All are in System32. The list is: conhost, ntdll, kernel32, kernelbase, msvcrt, Conhostv2, combase, ucrtbase, RPCRT4, bcryptPrimitives, GDI32, gdi32full, USER32, win32u, IMM32, OLEAUT32, msvcp_win, PROPSYS, sechost, shcore, SHELL32, cfgmgr32, windows.storage, powerprof, advapi32, shlwapi, kernel.appcore, and profapi.

UPDATE:

Seems similar to (if not the same as) ASP.NET Core ILogger Memory Leak on Windows 10 (1607) / Windows Server 2016 . Unfortunately that also lacks answers.

Does your ASP.NET application create any subprocesses (Typically with Process.Start() but there are other ways)? Would the executables it is spawning as subprocesses happen to be console applications? — Ben Voigt
@BenVoigt yes the subprocess spawns is a console application. — ChaseMedallion
@BenVoigt any theory as to why that would cause conhost.exe to leak? The subprocess itself does not seem to be leaking memory. — ChaseMedallion
You can check the dll attached to this conhost.exe process (using Process Explorer tool from sysinternals for example) see if anything looks suspicious (3rd party dll, etc.) — Simon Mourier
@ChaseMedallion Sorry for the late reply, I posted an answer how to fix the issue I had: stackoverflow.com/a/68577179/779506 OS version is indeed relevant, thus if your issue is only happening on Server 2016 this might be related. — sky

ChaseMedallion ChaseMedallion · Accepted Answer · 2021-10-18T16:57:51

This turned out to be a Windows OS bug. We contacted Microsoft support about the issue and received a patch (likely the same patch mentioned by @sky in stackoverflow.com/a/68577179/779506).

conhost.exe seemingly leaking memory

1 Answers